The present invention relates to a process for preparing olefinic living polymers, and more particularly to a process for preparing olefinic living polymers which can be converted into terminal-functionalized polymers and block copolymers having a narrow molecular weight distribution.
Regarding living polymerization of olefins, there are reported production of syndiotactic polypropylene (PP) ([r] not more than 0.8) having a molecular weight distribution (Mw/Mn) of 1.05 to 1.4 using V(acac)3/R2AlX catalyst, wherein acac is acetylacetonato, R is ethyl or isobutyl group and X is Cl or Br, in Macromolecules, 12, 814(1979); production of living polymers of ethylene or 1-hexene using Me2Si(2-SiMe3-4-tBu-C5H2)2Sm(THF)2 catalyst.without cocatalyst, wherein Me is methyl group, tBu is t-butyl group and THF is tetrahydrofuran, in Shokubai, 37, 205(1995); production of living polymers of C6 to C10 xcex1-olefins having a Mw/Mn ratio of not more than 1.1 at room temperature using [(2,6-iPr2C6H3)N(CH2)3N(2,6-iPr2C6H3)]TiMe2/B(C6F5)3 catalyst, wherein iPr is isopropyl group and Me is methyl group, in J. Am. Chem. Soc., 118, 10008(1996); living polymerization of xcex1-olefins having 3 to 18 carbon atoms in a low concentration at a temperature of not more than 0xc2x0 C. in the presence of a catalyst system consisting of a bulky aryl group-containing diimine complex of Ni represented by the formula: 
wherein Ar is 2,6-diisopropylphenyl group, in J. Am. Chem. Soc., 118, 11664(1996); production of atactic living polymer of 1-hexene having a Mw/Mn ratio of not more than 1.1 at 0xc2x0 C. using a catalyst consisting of a tri-coordination type diamide complex of Zr ([NON]ZrMe2 complex) and B(C6F5)3 wherein [NON]ZrMe2 complex is a compound of the formula: 
in J. Am. Chem. Soc., 119, 3830(1997); and production of syndiotactic living polypropylene of [r] about 0.65 at low temperatures using [tBuNSiMe2Flu]TiMe2/B(C6F5)3 catalyst, wherein tBu is t-butyl group, Me is is methyl group and Flu is 
in Polym. Prepr., Japan, 46, 1601(1997); cf. Kobunshi, Vol. 47, February, 74-77(1998).
Also, JP-A-5-503546 discloses production of a multi-block copolymer having a molecular weight distribution of 1.4 to 1.8 by bringing a first olefin component into contact with a catalyst which is a reaction product of a metallocene component such as a bis(cyclopentadienyl)titanium, zirconium or hafnium derivative (first component) with a second component having a cation capable of donating a proton and a compatible non-coordinating anion, at a temperature of xe2x88x925 to +10xc2x0 C. to produce a first living polymer and then adding a second monomer to copolymerize with the first polymer.
Further, JP-A-9-500150 discloses production of a block copolymer or tapered copolymer having a molecular weight distribution of 1.35 to 4.1 by copolymerizing at least one olefinic monomer at a temperature of xe2x88x925 to +10xc2x0 C. using a catalyst which is a reaction product of a cyclopentadienyl Group IV-B metal component with an alumoxane or a compatible non-coordinating anion wherein Ti, Zr and Hf are exemplified as the Group IV-B metal.
On the other hand, it is reported in Macromelecules, 31, 3184(1998) that living polymerization of propylene or 1-hexene takes place at xe2x88x9250xc2x0 C. in the presence of [tBuNSiMe2Flu]TiMe2 catalyst.
For example, however, in case of using the [(2,6-iPr2C6H3)N(CH2)3N(2,6-iPr2C6H3)]TiMe2/B(C6F5)3 catalsyt or the bulky aryl group-containing diimine Ni complex/methylaluminoxane catalyst mentioned above, problems are encountered that these catalysts are complicated and are hard to prepare and the obtained polymers are poor in regularity. The production of syndiotactic living polymers at low temperatures using the above-mentioned [tBuNSiMe2Flu]TiMe2/B(C6F5)3 catalyst has also the problems that syndiotactic polymers having a low stereoregularity are only obtained, and polymers having a high stereoregularity such as high syndiotacticity or high isotacticity, polymers rich in isotacticity or atactic polymers cannot be obtained, and that the structure of the catalyst is complicated and it is hard to prepare the catalyst.
Also, in case of using as a catalyst the reaction product of a metallocene component and a second component having a cation capable of donating a proton and a compatible non-coordinating anion, and in case of using as a catalyst a reaction product of a cyclopentadienyl Group IV-B metal component with an alumoxane or a compatible non-coordinating anion, it is not always possible to make the molecular weight distribution narrow or it is not always possible to efficiently obtain living polymers. In the field of using terminal-functionalized polymers or block copolymers, it has been desired to produce living polymers having a narrower molecular weight distribution or to more efficiently produce living polymers, from the viewpoint that polymers having a high rate of terminal functionalization or a high blocking efficiency.
Further, the living polymerization at xe2x88x9250xc2x0 C. using [tBuNSiMe2Flu]TiMe2 catalyst is not satisfactory in yield and molecular weight of the produced polymers.
The present inventors have found, as a result of making intensive study in order to solve the above problems of the prior art, that olefinic living polymers having a molecular weight distribution of not more than 1.3 can be prepared when olefinic monomers are polymerized at low temperatures using a catalyst comprising a hafnium or zirconium-containing compound having one or two cyclopentadienyl backbones, a borane or borate compound having a phenyl group which may be substituted, and optionally a specific alkylaluminum compound.
Thus, in accordance with an embodiment of the present invention, there is provided a process for preparing olefinic living polymers which comprises polymerizing an olefinic monomer having 2 to 20 carbon atoms at a polymerization temperature of xe2x88x9220 to xe2x88x92100xc2x0 C. in the presence of a catalyst comprising:
(A-1) a hafnium-containing compound having one or two cyclopentadienyl backbones, and
(B) a borane compound (B-1) of the formula (I):
B(Ph)3xe2x80x83xe2x80x83(I)
xe2x80x83wherein Ph is a phenyl group which may be substituted, or
a borate compound (B-2) of the formula (II):
Bxe2x88x92(Ph)4X+xe2x80x83xe2x80x83(II)
xe2x80x83wherein Ph is as defined above and X+ is a cation, to produce a polymer having a molecular weight distribution (Mw/Mn) of 1 to 1.3.
Further, in accordance with another embodiment of the present invention, there is provided a process for preparing olefinic living polymers which comprises polymerizing an olefinic monomer having 2 to 20 carbon atoms, at a polymerization temperature of xe2x88x9260 to xe2x88x92100xc2x0 C. in the presence of a catalyst comprising:
(A-2) a zirconium-containing compound having one or two cyclopentadienyl backbones, and
(B) a borane compound (B-1) of the formula (I):
B(Ph)3xe2x80x83xe2x80x83(I)
xe2x80x83wherein Ph is a phenyl group which may be substituted, or
a borate compound (B-2) of the formula (II):
Bxe2x88x92(Ph)4X+xe2x80x83xe2x80x83(II)
xe2x80x83wherein Ph is as defined above and X+ is a cation, to produce a polymer having a molecular weight distribution (Mw/Mn) of 1 to 1.3.
In the preparation of the catalyst, the hafnium-containing compound (A-1) and the zirconium-containing compound (A-2) may be used together. In this case, there is the case that living polymers having a bimodal molecular weight distribution are obtained.
The above-mentioned catalysts can be prepared by using the components (A) and (B) together with an aluminum compound (C) of the formula (III):
AlR3xe2x88x92nYnxe2x80x83xe2x80x83(III)
wherein R is a hydrocarbon group having 4 to 20 carbon atoms, Y is a halogen atom, an alkoxyl group, a trialkylsiloxy group, a di(trialkylsilyl)amino group or a trialkylsilyl group, and n is 0, 1 or 2. The aluminum compound (C) serves as a so-called scavenger (agent for scavenging impurities), and catalysts comprising the components (A) to (C) stably produce living polymers even in polymerization systems containing impurities.
Thus, in accordance with still another embodiment of the present invention, there is provided a process for preparing olefinic living polymers which comprises polymerizing an olefinic monomer having 2 to 20 carbon atoms in the presence of a catalyst comprising:
(A) a hafnium or zirconium-containing compound having one or two cyclopentadienyl backbones,
(B) a borane compound (B-1) of the formula (I):
B(Ph)3xe2x80x83xe2x80x83(I)
xe2x80x83wherein Ph is a phenyl group which may be substituted, or
a borate compound (B-2) of the formula (II):
Bxe2x88x92(Ph)4X+xe2x80x83xe2x80x83(II)
xe2x80x83wherein Ph is as defined above and X+ is a cation, and
(C) an aluminum compound of the formula (III):
xe2x80x83AlR3xe2x88x92nYnxe2x80x83xe2x80x83(III)
wherein R is a hydrocarbon group having 4 to 20 carbon atoms, Y is a halogen atom, an alkoxyl group, a trialkylsiloxy group, a di(trialkylsilyl)amino group or a trialkylsilyl group, and n is 0, 1 or 2, to produce a polymer having a molecular weight distribution (Mw/Mn) of 1 to 1.3.
In case of using the hafnium catalyst, the living polymerization temperature is from xe2x88x9220 to xe2x88x92100xc2x0 C., preferably from xe2x88x9230 to xe2x88x9280xc2x0 C., more preferably from xe2x88x9240 to xe2x88x9280xc2x0 C. In case of using the zirconium catalyst, the living polymerization temperature is lower as compared with the hafnium catalyst and is usually from xe2x88x9260 to xe2x88x92100xc2x0 C., preferably from xe2x88x9260 to xe2x88x9280xc2x0 C.
The present inventors have also found, as a result of further investigation about the zirconium catalyst, that the living polymerization is can be carried out at a higher temperature when the zirconium catalyst is prepared by using the zirconium-contawning compound (A-2), the boron compound (B) and optionally the aluminum compound (C) together with a titanium-containing compound (D).
Thus, the present invention further provides a process for preparing olefinic living polymers which comprises polymerizing an olefinic monomer having 2 to 20 carbon atoms at a polymerization temperature of xe2x88x9220 to xe2x88x92100xc2x0 C. in the presence of a catalyst comprising:
(A-2) a zirconium-containing compound having one or two cyclopentadienyl backbones,
(B) a borane compound (B-1) of the formula (I):
B(Ph)3xe2x80x83xe2x80x83(I)
xe2x80x83wherein Ph is a phenyl group which may be substituted, or
a borate compound (B-2) of the formula (II):
Bxe2x88x92(Ph)4X+xe2x80x83xe2x80x83(II)
xe2x80x83wherein Ph is as defined above and X+ is a cation,
(D) a titanium-containing compound, and optionally
(C) an aluminum compound of the formula (III):
AlR3xe2x88x92nYnxe2x80x83xe2x80x83(III)
xe2x80x83wherein R is a hydrocarbon group having 4 to 20 carbon atoms, Y is a halogen atom, an alkoxyl group, a trialkylsiloxy group, a di(trialkylsilyl)amino group or a trialkylsilyl group, and n is 0, 1 or 2.
Preferably, the titanium-containing compound (D) is a titanium-containing compound having one cyclopentadienyl backbone.
The polymerization is carried out preferably at a temperature of xe2x88x9230 to xe2x88x9280xc2x0 C., especially xe2x88x9240 to xe2x88x9260xc2x0 C.
The polymerization catalyst according to the present invention is formed, for example, by mixing the respective components which constitute the catalyst in a predetermined ratio in a solvent at a temperature not higher than room temperature. The catalyst according to the present invention is applicable to homopolymerization of an olefin and copolymerization of at least two olefins, and can produce living polymers having a narrow molecular weight distribution.